Ankle braces for inhibiting inversion and eversion of the ankle while permitting relatively uninhibited plantar flexion and dorsiflexion of the foot, or for controlling plantar flexion and/or dorsiflexion, have been available for many years, indeed since at least the turn of the century.
With the advent of modern materials of construction, especially plastics, the braces have become lighter, less cumbersome, more easily fitted to and removed from the leg and ankle, and better adapted to the performance of their intended functions.
Of late, one ankle brace that has acquired particular acceptance is the so-called stirrup ankle brace, representative examples of which are illustrated in the patent to Glenn W. Johnson, Jr. U.S. Pat. No. 4,280,489 and the patent to Tracy Grim U.S. Pat. No. 4,844,094. As shown by these patents, the brace comprises a base member on which the heel of the wearer rests, a pair of rigid side members hingedly connected to opposite sides of the base member and extending upwardly on opposite sides of the ankle and along the lower leg, a pair of cushioning pads respectively coextensive with and secured to the inner surfaces of the side members for cushioning the leg and ankle, and a pair of leg encircling straps adapted to be wrapped about the lower leg and the two side members to hold the side members in place with the pads firmly and snugly engaging the opposite sides of the leg and ankle.
When applied to the leg and ankle, the side members inhibit inversion and eversion, i.e., twisting, of the ankle, but the brace is open to the front and rear and thereby permits normal plantar flexion and dorsiflexion. The brace is designed to be received in a conventional shoe, whereby the wearer may engage in normal activities, such as walking, running and sports activities, while the ankle is protected against inversion and eversion. The Grim patent also provides a counter strap at the achilles tendon and eyelets on the front edges of the side members so that the brace can be tied to the wearer's shoe by the lace of the shoe, thereby to gain further support.
While the stirrup ankle brace is an effective product which has gained wide acceptance, it does suffer a problem referred to as "pistoning". Specifically, because the side members are of necessity hingedly connected to the base member (so that the side members can be swung into engagement with the leg and ankle), the two side members tend to reciprocate vertically up and down in an alternating relationship to one another, much like the pistons of an internal combustion engine, thus the term "pistoning". This is, of course, a source of irritation to the wearer and detracts from the effectiveness of the brace.
Also, problems are frequently encountered in fitting the side members to the leg. Inasmuch as the two side members are independently movable, and the two leg encircling straps are the only means provided for locating each side member relative to the leg and for holding the side members in place relative to one another and the leg, it is necessary for each of the straps to be secured to both of the side members and for at least one of the points of securement to be adjustable. This is customarily accomplished by forming the straps from a fabric having a plush surface and by securing patches of fabric hook material (such as the well known product sold under the trademark "VELCRO" and equivalents thereof) to the exterior surfaces of both of the side members for releasable locking engagement with the plush surfaces of the strap. Due to the necessity for locking both of the side members to the straps, the tension on a given strap around the circumference of the leg is rarely uniform, i.e., the tension on the portion of the strap passing between the side members posteriorly of the leg is frequently different from the tension on the portion of the strap passing between the side members anteriorly of the leg. Also, the tension on the two straps is frequently different. This in turn can result in a poor fit, further detracting from the effectiveness of the brace.